Le mal de pays

In French there are a number of ways to express this concept:
– nostalgique = homesick (adj)
– avoir le mal de pays = to be homesick (for a place/country)
– s’ennuyer de (sa famille) = to be homesick (for one’s family)
– avoir la nostalgie (de qch) = to be homesick (for something)

Example
L’odeur de l’herbe lui donna la nostalgie de la ferme de ses parents.The smell of the grass made her homesick for her parents’ farm.

The Welsh word for homesickness is hiraeth /hɪəraɪ̯θ/, which is apparently one of those words that is untranslatable. It means homesickness tinged with grief or sadness over the lost or departed. It is a mix of longing, yearning, nostalgia, wistfulness, and the earnest desire for the Wales of the past. It has similarities to saudade in Portuguese and morriña in Galician [source].